From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-8.3 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id F3115C2D0E7 for ; Fri, 27 Mar 2020 09:59:06 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id C048D20578 for ; Fri, 27 Mar 2020 09:59:06 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=web.de header.i=@web.de header.b="FOMeTWdR" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727185AbgC0J7F (ORCPT ); Fri, 27 Mar 2020 05:59:05 -0400 Received: from mout.web.de ([212.227.17.11]:48729 "EHLO mout.web.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726027AbgC0J7F (ORCPT ); Fri, 27 Mar 2020 05:59:05 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=web.de; s=dbaedf251592; t=1585303125; bh=3sJu9fUArkbibaP7WFaKAEzBqN+q83Qrxfjqw40JE6M=; h=X-UI-Sender-Class:Subject:To:Cc:References:From:Date:In-Reply-To; b=FOMeTWdRP5Eq/kmssOzWMXzpWckepwiZa8XLZnpzSmVHwM/Wpzli/svaTVQCA8KRs FdBtlRpT/mnjCrt1aLSZfG9jMCto/q+8HKIStBsiVgtM/nHTWoewJw1Xheq/REYPOl 9sFNduTJJIsIMdb4sZh76/GwWiKv7Yxj+OxI7Is8= X-UI-Sender-Class: c548c8c5-30a9-4db5-a2e7-cb6cb037b8f9 Received: from [192.168.1.10] ([95.157.55.156]) by smtp.web.de (mrweb101 [213.165.67.124]) with ESMTPSA (Nemesis) id 0Le4Lg-1jaMzw3m0K-00psvk; Fri, 27 Mar 2020 10:58:45 +0100 Subject: Re: [PATCH] swiotlb: Allow swiotlb to live at pre-defined address To: Alexander Graf , iommu@lists.linux-foundation.org Cc: Konrad Rzeszutek Wilk , x86@kernel.org, Christoph Hellwig , Marek Szyprowski , Robin Murphy , linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, Mark Rutland , dwmw@amazon.com, benh@amazon.com, alcioa@amazon.com, aggh@amazon.com, aagch@amazon.com, dhr@amazon.com References: <20200326162922.27085-1-graf@amazon.com> From: Jan Kiszka Message-ID: <9ff68753-20d1-62b1-6250-91ed4beb1bde@web.de> Date: Fri, 27 Mar 2020 10:58:43 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.6.0 MIME-Version: 1.0 In-Reply-To: <20200326162922.27085-1-graf@amazon.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: quoted-printable X-Provags-ID: V03:K1:PdNtUhVPObC1NxI5ax+8GQe3v47vjTq4mEi/59bmOUWMu8JZqRT TNsTyDMgV8WUeg5bRVyv6+8YkM5TSW3rx1+/2MwfU3JfQDCCwUpNZyLngpOBHLtQ4yZEokN 9Srm+Yp8CXFi0oImvFpp+VZZAGxD/8rob6pQYSNrIwWC6pwbq78YBDWjj7y5Wvtw/FICW73 39eDdNmuXDeVlwXfDcYww== X-UI-Out-Filterresults: notjunk:1;V03:K0:yc+0mO+tq5w=:bs26ghpzYfEHeSNgiR/cxk qn5cFDWow2uB1Q8hzYS++4jk6MRQO1NS24MjTgkFukmI7h8blEstF1DgaQ+pvkrAMMipH97HK fRYwtiLvE0wE7Qdmxd+63EodXC9wP0zjEVTnxQq7P63BazGxO7S0GLEJByvuh/6HS62tv9ew+ P0CZ5P/rkald9bPj7rXArwRwxZDUbsK5qIVMpJpBWqYVgUkjkGiFHv5GxWqJPYjxvL4f9nyxV bcuWFVS6I6UlGhM/1IvUZLAsV876+nRRUAiQ7V8GNEsjFy7SEj/A2okKv9Mi+bEs3iYBSeD5R DDar4nrE65D+blKX6CAz+cEiZMYaVhkK8ddqp4i0/3t68qD1G0NuIGOpleI34oq4qIRuzAfab CErKH/UXBkqk8XEJMeLimQEMTepz5+7fbVCONVwx5NI68RPm+LApdueKgIyUiGzWn5ve5mGya oUP1T50PaRofQ1vUilOpVC8muIum2t/wcK/e5Y7t9148BXSZr4rKdgMBff58N7nmGIQBXJyTK 8DmcLFDLKHF1xAS/ItRytGalJ0+h0kXhdYF2t9Z/4boqcJ3dbaWSoz3DuKzUY2oYfI1hwMOoz nvcNGmt1DMbG4JQ3tt8mA/KT/Q5jVec2cuKOGvTzQOKM0Q6CUeZ/QMaRutpFiel+o6k98yAb7 KlzYXFnSCuHVAvzVwvSUhizU2nF/1xmEPFXNQxhRgAt1tLJzLekBZ5qe3eNtxg6NHyP6N7v0I lQFIX9Tm4Eg1eCXl2TfY9KoQKq53vF/V2ThhYoLEL7DOohCVWQ17Fo3YRilwON7SnR/5W+SCk S4Tg2OWiJ7n5MU97jWlSKewChMlCGJW2qqCODzZ82EKVsBjGuZacJk8HAdE6xmQAtUnuTv5xH uq1fm92lH90rv2WMJM0u9N4EnWy/Ez/yF+wi9Yu42IAqJxHKaLoqjZqRShcIich0MZJKq40K0 lgfE3qrxeGvNE9dTl9TaFGmYkeWgZeFMhUXeWdmpORU26MdBA7exRoJuBRLQPCjoYEa5d+fLR aYtTLh7cMroAFgn/pVi0EjLIkYH1XHR7qj46p0yB4Fjwo794q3JWWfrp7mNMmByyNH7UdZWjz VYfQwQA/1KrBbFzNjYelnSyHT6cNRTgF+MIo2kGzSVFkrA3tfUnNzeEl1tHFqSpVM9wKXayd1 6MEqAK50K4x2Y+yYcNGJmwb5SzULGS2h6LW6i8meC6OBSI69+U3sc5M+NxkDCMmrFlkNRzzfK diZRZZ8kpd4amq0dq Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 26.03.20 17:29, Alexander Graf wrote: > The swiotlb is a very convenient fallback mechanism for bounce buffering= of > DMAable data. It is usually used for the compatibility case where device= s > can only DMA to a "low region". > > However, in some scenarios this "low region" may be bound even more > heavily. For example, there are embedded system where only an SRAM regio= n > is shared between device and CPU. There are also heterogeneous computing > scenarios where only a subset of RAM is cache coherent between the > components of the system. There are partitioning hypervisors, where > a "control VM" that implements device emulation has limited view into a > partition's memory for DMA capabilities due to safety concerns. > > This patch adds a command line driven mechanism to move all DMA memory i= nto > a predefined shared memory region which may or may not be part of the > physical address layout of the Operating System. > > Ideally, the typical path to set this configuration would be through Dev= ice > Tree or ACPI, but neither of the two mechanisms is standardized yet. Als= o, > in the x86 MicroVM use case, we have neither ACPI nor Device Tree, but > instead configure the system purely through kernel command line options. > > I'm sure other people will find the functionality useful going forward > though and extend it to be triggered by DT/ACPI in the future. > > Signed-off-by: Alexander Graf > --- > Documentation/admin-guide/kernel-parameters.txt | 3 +- > Documentation/x86/x86_64/boot-options.rst | 4 ++- > kernel/dma/swiotlb.c | 46 +++++++++++++++++= ++++++-- > 3 files changed, 49 insertions(+), 4 deletions(-) > > diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documenta= tion/admin-guide/kernel-parameters.txt > index c07815d230bc..d085d55c3cbe 100644 > --- a/Documentation/admin-guide/kernel-parameters.txt > +++ b/Documentation/admin-guide/kernel-parameters.txt > @@ -4785,11 +4785,12 @@ > it if 0 is given (See Documentation/admin-guide/cgroup-v1/memory.rs= t) > > swiotlb=3D [ARM,IA-64,PPC,MIPS,X86] > - Format: { | force | noforce } > + Format: { | force | noforce | addr=3D } > -- Number of I/O TLB slabs > force -- force using of bounce buffers even if they > wouldn't be automatically used by the kernel > noforce -- Never use bounce buffers (for debugging) > + addr=3D -- Try to allocate SWIOTLB at defined address > > switches=3D [HW,M68k] > > diff --git a/Documentation/x86/x86_64/boot-options.rst b/Documentation/x= 86/x86_64/boot-options.rst > index 2b98efb5ba7f..ca46c57b68c9 100644 > --- a/Documentation/x86/x86_64/boot-options.rst > +++ b/Documentation/x86/x86_64/boot-options.rst > @@ -297,11 +297,13 @@ iommu options only relevant to the AMD GART hardwa= re IOMMU: > iommu options only relevant to the software bounce buffering (SWIOTLB)= IOMMU > implementation: > > - swiotlb=3D[,force] > + swiotlb=3D[,force][,addr=3D] > > Prereserve that many 128K pages for the software IO bounce buf= fering. > force > Force all IO through the software TLB. > + addr=3D > + Try to allocate SWIOTLB at defined address > > Settings for the IBM Calgary hardware IOMMU currently found in IBM > pSeries and xSeries machines > diff --git a/kernel/dma/swiotlb.c b/kernel/dma/swiotlb.c > index c19379fabd20..83da0caa2f93 100644 > --- a/kernel/dma/swiotlb.c > +++ b/kernel/dma/swiotlb.c > @@ -46,6 +46,7 @@ > #include > #include > #include > +#include > > #define CREATE_TRACE_POINTS > #include > @@ -102,6 +103,12 @@ unsigned int max_segment; > #define INVALID_PHYS_ADDR (~(phys_addr_t)0) > static phys_addr_t *io_tlb_orig_addr; > > +/* > + * The TLB phys addr may be defined on the command line. Store it here = if it is. > + */ > +static phys_addr_t io_tlb_addr =3D INVALID_PHYS_ADDR; > + > + > /* > * Protect the above data structures in the map and unmap calls > */ > @@ -119,11 +126,23 @@ setup_io_tlb_npages(char *str) > } > if (*str =3D=3D ',') > ++str; > - if (!strcmp(str, "force")) { > + if (!strncmp(str, "force", 5)) { > swiotlb_force =3D SWIOTLB_FORCE; > - } else if (!strcmp(str, "noforce")) { > + str +=3D 5; > + } else if (!strncmp(str, "noforce", 7)) { > swiotlb_force =3D SWIOTLB_NO_FORCE; > io_tlb_nslabs =3D 1; > + str +=3D 7; > + } > + > + if (*str =3D=3D ',') > + ++str; > + if (!strncmp(str, "addr=3D", 5)) { > + char *addrstr =3D str + 5; > + > + io_tlb_addr =3D kstrtoul(addrstr, 0, &str); > + if (addrstr =3D=3D str) > + io_tlb_addr =3D INVALID_PHYS_ADDR; > } > > return 0; > @@ -239,6 +258,25 @@ int __init swiotlb_init_with_tbl(char *tlb, unsigne= d long nslabs, int verbose) > return 0; > } > > +static int __init swiotlb_init_io(int verbose, unsigned long bytes) > +{ > + unsigned __iomem char *vstart; > + > + if (io_tlb_addr =3D=3D INVALID_PHYS_ADDR) > + return -EINVAL; > + > + vstart =3D memremap(io_tlb_addr, bytes, MEMREMAP_WB); > + if (!vstart) > + return -EINVAL; > + > + if (swiotlb_init_with_tbl(vstart, io_tlb_nslabs, verbose)) { > + memunmap(vstart); > + return -EINVAL; > + } > + > + return 0; > +} > + > /* > * Statically reserve bounce buffer space and initialize bounce buffer= data > * structures for the software IO TLB used to implement the DMA API. > @@ -257,6 +295,10 @@ swiotlb_init(int verbose) > > bytes =3D io_tlb_nslabs << IO_TLB_SHIFT; > > + /* Map IO TLB from device memory */ > + if (!swiotlb_init_io(verbose, bytes)) > + return; > + > /* Get IO TLB memory from the low pages */ > vstart =3D memblock_alloc_low(PAGE_ALIGN(bytes), PAGE_SIZE); > if (vstart && !swiotlb_init_with_tbl(vstart, io_tlb_nslabs, verbose)) > To make this useful also for shared-memory based devices, it should not only have a command-line independent interface. Multi-instance support would be needed so that you can attach swiotlb with individual address ranges to devices that need it and leave it alone for other that do not (e.g. passed-through guest devices). Jan